Original *kw was lost before back vowels in Latin, as in *sekwondos > secundus ‘following, next’, *kwolō > colō ‘I cultivate’, in the second half of the third century BC (Reference MeiserMeiser 1998: 92; Reference WeissWeiss 2020: 165).Footnote 1 The spelling with <qu> was maintained (or reintroduced) in some words (e.g. equus ‘horse’, aequus ‘equal’, on the basis of parts of the paradigm where /kw/ occurred before a non-back vowel; quottidiē ‘every day’, which is attested later than cottidiē,Footnote 2 Reference Ernout and MeilletErnout and Meillet 1985: 146), notably in quom for cum ‘when, since’ < *kwom (and by extension, also for cum ‘with’ < *kom). The spelling quom is found frequently in epigraphic texts of the first century BC and earlier, and there are still occasional examples in the first century AD and later.Footnote 3 An ‘original texts’ search on EDCS for ‘ cum ’ (date range ‘1’ to ‘400’, 29/09/2022) finds 4,489 inscriptions containing cum. Such a small number of instances suggests that the spelling was old-fashioned by the first century AD, and this is likely to be all the more true for other spellings with <qu>.
Velius Longus and Curtius Valerianus confirm the view that on the whole the <qu> spellings are old-fashioned:
‘q’ quoque littera facit differentiam uocum ab antiquis maxime obseruata<m>. <nam ‘cum’> quotiens pro aduerbio temporis scribebant, ‘q’ littera utebantur; <quotiens> pro praepositione, ‘c’ ponebant. aliud est ‘cum subito adsurgens’, aliud ‘cum fluctu’. et haec pronomina, ‘cuius’ et ‘cui’, per ‘q’ censuerunt quidam scribenda, quo magis seruaretur origini fides, ut, quomodo ‘quis’ inciperet a ‘q’, si<c> ‘quius’ ‘qui’. hoc amplius, quo pinguior esset enuntiatio, ‘o’ quoque inserebant et per ‘quo’ ‘quoius’ ‘quoi’ scribebant. nos ad breuitatem festinauimus scribendi et illam pinguitudinem limare maluimus, tam hercule quam ‘cur’ magis <scribimus quam ‘quor’> quod genus est ἐτυμολογίας.
Also the ancients used the letter q very much to make a distinction between words. Whenever they used to write cum, in the sense of a temporal adverb, they used the letter q; whenever they used it as a preposition they spelt with c. Because ‘when (cum) suddenly rising up’ is a different thing from ‘with (cum) the tide’. And some of them thought that the pronoun forms cuius and cui should be spelt with q, the better to faithfully represent their origins, so that, just as quis begins with q, so should quius and qui. Furthermore, so that these words should be pronounced more fully, they also inserted an o and used to write quoius and quoi with the sequence quo. We in our hurry aim for brevity in writing and have preferred to file off such fullness, even going so far, by Hercules, as writing cur rather than quor, which is etymologically correct.
item ‘cui’ utrum per ‘q’ an per ‘c’ debeat scribi, quia non nulli inuenti sunt qui ‘q’ littera<m> illo catholico tuerentur, quod in nulla uoce per declinationem prima littera immutetur. ita cum sit ‘quis’, ‘quius’ et ‘qui’ per ‘q’ litteram censent scribendum.
Likewise, whether cui ought to be written with ‘q’ or ‘c’, because a number of people can be found who maintain the letter ‘q’, on the general rule that in no word does declension take place by changing the first letter. So, since it is quis, they think one should write quius and qui, with the letter ‘q’.
quasdam uero scriptiones antiquis relinquamus, ut in eo quod est ‘cur’. illi enim per ‘quor’ scribebant, ut supra dixi, nam et ipsum ‘cui’ per ‘quoi’, quo pinguius sonaret. <nos> contenti sumus per ‘cur’ scribere …
But let us leave certain spellings to the ancients, as in the case of cur. Because they used to spell it quor, as I have said above, and even cui as quoi, so that it might have a fuller sound. We are content to write cur …
‘cur’ alii per c scribendum putauerunt dicentes non posse q litteram poni, ubi u esset sine alia uocale, secundum regulam supradictam; alii per q, eo quod originem trahat ab interrogatiuis aduerbiis, quae sunt ‘quando’, ‘quorsum’. usus autem obtinuit ut ‘cur’ per c scribatur.
Some have thought that cur ought to be written with c on the grounds that q should not be used when it is followed by u but no other vowel, according to the rule I have previously discussed; others that it should be written with q, on the grounds that it has the same origin as the interrogative adverbs, such as quando and quorsum. But usage has won out, so that cur is written with c.Footnote 4
However, Curtius Valerianus (in Cassiodorus, De orthographia 3.3–4) and Marius Victorinus make an exception for cum as a temporal adverb, recommending a (rather artificial) spelling quum. But the spelling quom (unmentioned by Curtius Valerius) is too old-fashioned for Marius Victorinus:
‘cum’ aduerbium temporis antiqui quattuor litteris scribebant [in] his, q u u m; apud Catonem ‘quum’ rursus per o, ‘quom’ … item ‘cuius’ per q u o i u s litteras scribebant. de quibus ne plura scribam, hoc custodite, ut, cum fuerit aduerbium temporis, per q u siue unum siue duo scribatis, ut ‘qum primum’ et ‘quum hoc facerem’.
The ancients used to write cum as a temporal adverb with four letters, as quum; Cato even took the spelling further back in time with o: quom … Likewise they used to write cuius as quoius. So as not to say anything more about these words, take care that when it is a temporal adverb, you write it with qu or quu, as in qum primum ‘when first’ and quum hoc facerem ‘when I was doing this’.
Terentius Scaurus, however, does not rule out quom as old-fashioned:
‘cum’ quidam per ‘cum’, nonnulli per ‘quom’. quidam etiam esse differentiam putant, quod praepositio quidem per ‘c’: ‘<cum> illo’, ‘cum Claudio’, ‘cum Camillo’; aduerbium autem per ‘q’ debeat scribi, ut ‘quom legissem’, ‘quom fecissem’, quoniam antiqui pro hoc aduerbio †cuine† dicebant …
For cum some people write cum, others quom. There are even some who think that the difference is that the preposition should be spelt with c, as in cum illo ‘with him’, cum Claudio ‘with Claudius’, cum Camillo ‘with Camillus’; but the adverb should be spelt quom, as in quom legissem ‘when I had read’, quom fecissem ‘when I had done’, since the ancients used to say †cuine† for this adverb …
Caesellius Vindex recommends not only quum but also quiusque for cuiusque:
‘cum’ praepositio per c scribenda est; ‘quum’ aduerbium temporis, quod significat ‘quando’, per q scribendum est discretionis causa … ‘quuiusque’ non per c scribitur, sed per q …
The preposition cum ought to be spelt with c; the temporal adverb quum, which means ‘when’, ought to be written with q in order to distinguish it from cum … quuiusque ought not to be written with c but with q …
In line with most of the writers on language, spellings with <qu> are infrequent in the corpora. Although cum is a common word across these texts, we find quom ‘when, since’ only in a letter written by a scribe at Vindolanda (Tab. Vindol. 248) and qu[u]m or qu[o]m in a Claudius Tiberianus letter (P. Mich. VIII 472/CEL 147).Footnote 5 At Vindolanda we also find q̣uụr (Tab. Vindol. 652) for cūr ‘why’ in a fragmentary letter whose writer is unidentifiable, although as they use an apex they are likely to be a scribe (see pp. 226–32).
There appears to be a hypercorrect use of <qu> in laqụonecoru (CEL 225), presumably for lacōnicōrum ‘steam baths’, in a papyrus letter of the fourth century AD from Karanis in Egypt, apparently a petition of some sort whose writer shows some substandard features.Footnote 6 Curiously, there are also hypercorrect examples before <a> in a pair of curse tablets from Baetica in the first century BC: omut[e]sq[ua]nt (Kropp 2.2.3/4), [om]utesquant, [omut]esquant (2.2.3/5) for obmūtescant ‘may they become dumb’.
This evidence suggests that while use of <qu> in these contexts was old-fashioned and uncommon, it did survive within some educational traditions for quite some time, although its restriction to words in which it was etymologically correct was not necessarily well learnt or taught.Footnote 7